The handle was originally 19mm thick, 39mm wide, and slightly rounded at the sides. I found that the handle was uncomfortably wide, and wanted to reduce the width. The design is Tim's favorite bend in the handle just enough to not take set, bend in the mid limbs to take just a little set, and skiny stiff tips. I did not want to narrow the handle enough to bend much additionally because I did not want to loose weight. The target for handle width was 26mm instead of the original 39mm, or 2/3 of the original width. To maintain the original bend I should therefore make the handle thicker by the cube root of 3/2, or 115% of the original 19mm thickness. This would mean adding 2.8mm of thickness, and would be good for maintaining the bend, and weight, but increases the strain at the handle by 15% due to the extra thickness. In odrer to keep the handle strain at the same level as with the 39mm width the thickness has to be increased by the square root of 3/2, or to 123% of the original thickness, which is an extra 4.3mm. I decided on adding 4mm of red oak onto the handle to almost maintain the strain. This was supposed to result in an un-noticable increase in draw weight, and maintain the safety of the handle.
The bow is not 26mm wide, and 23mm thick, and went to 44# @ 25" after the modification, a 2# gain in weight. However, this may not due to the very slight extra handle stiffness. The bow has been living in a 25% humidity enforonment for the last 6 months, and I neglected to take a base line draw curve prior to the modification. It is likely that the extra weight is from the dhange in envoronemntal humidity from 55% ro 25%. ......I wish I had taken that curve.
The other surprise was that the bow popped a splinter on the first draw after the fix. I suppose I should have warmed the bow up before pulling to full draw, but I just yanked it back and heard that fatefull "tick. I say popped a splinter; a big splinter, about 18" long, and extending 2/3 across the back of the bow all the way down th the fades. I am glad I opted for keeping my safety margin or I might have had two bow halfs. As it is, I got another education in fixing split bows..........Thats right, never say die, I fixed it. Tight bond 3, lots of clamps, and 10 glue soaked linnen string bindings later, it has about 250 arrows thru it and seems OK. .......And the handle is nicer to shoot with now.
Here is the original width handle (39mm), and drawing on tape of the intended width reduction. The bottom picture is the 4mm tapered slab of wood added to the belly. Note that it needed to be flexed to match the already present belly thickness taper in the "fades" and handle.
Lots of clamps, and glue, and I had my extra wood on the belly. The bottom pic shows it with the clamps removed and sawed to the 26mm width.
Here is the last step, and the "finished" result. The top pic. is with 25% bevels in thickness, and width on both sides of the belly marked and cut. The bottom pic. is the finished rounded 26mm handle.
This is the result of the "shooting in". Nice little splinter.
The top pic here is the temp binding I put on the bow with it still braced so I could get it unstrung without further breakage. Lots of clamps and glue again. Then the finished fix with 3/8" wide bindings every 5 inches, just cause I don't trust the glue fix 100%.
Lastly the (I hope) finished form of the bow. The handle is now much nicer to shoot, and still works significantly. In spite of the split, the added thickness seems to be holding just fine.
<a href="http://www.flickr.com/pho.../63758724@N00/3006716895/" title="1800 oak splinter lift-3 by cedarwoodbear, on Flickr"><img src="http://farm4.static.flick...06716895_9ca56b0203_b.jpg" width="860" height="1024" alt="1800 oak splinter lift-3" /></a>
I hope this is instructive for anyone who wants to narrow a handle.